The Combustion Characteristics Of Ammonium Dinitramide Methanol Aqueous Solution And Its Applications

Ammonium dinitramide?ADN?is a water-soluble high-energy green inorganic salt with reduced toxicity and environmental impact.A promising way for developing the ADN-based liquid propellant is to dissolve the oxidant ADN in a methanol?CH₃OH?/water mixture.This kind of liquid propellant is considered to have the potential to replace the widely used monopropellant hydrazine and has applications in small space thrusters that control and adjust the orbits and attitudes of satellites.In this thesis,we investigated the combustion characteristics and applications of the ADN-based liquid propellant.Four major issues,including the evaporation and pyrolysis of the propellant from the liquid to the gas phase,the detailed mechanism of the gas-phase chemical reactions,the flame structure of the propellant and its combustion process in a small thruster of the attitude control engine,were investigated systematically by experimental and numerical methods.The evaporation and pyrolysis processes of the ADN-based liquid propellant from the liquid to the gas phase were investigated by a thermo-gravimetric analyzer and a Curie point pyrolysis unit,under slow and rapid heating rates,respectively.And the gas-phase products were detected and measured by a Fourier transform infrared spectroscopy.The results showed that during the phase transition from the liquid to the gas,methanol and water evaporated from the propellant,while ADN decomposed.The evaporation process of methanol and the decomposition process of ADN were not synchronous.To analyze the combustion process of the ADN-based liquid propellant,a detailed gas-phase ADN-CH₃OH chemical reaction mechanism was established,containing 50 components and235 reactions.In this mechanism,the interaction between ADN and methanol is accom-plished through the oxidation process of methanol and other carbonous compounds by the ADN decomposition products.This chemical mechanism was verified by comparing the numerical results with the existed experimental data.Furtherly,a model combustion experiment system for the ADN-based liquid propel-lant was built,refering to the structure and size of the real thruster.With the help of this experiment system,we used the deionized water as the medium to test the atomization ef-fect of the injector and investigated the liquid flowing process in the catalytic bed?porous media?.In the combustion experiment of the propellant at 1 atm,we investigated the flame propagation process in the catalytic bed and the flame structere in the downstream combustion chamber,measuring the flame axial temperature distribution.By comparing the experimental results with the premixed flame numerical results based on the detailed gas-phase chemical mechanism,the flame structure of the ADN-based liquid propellant was concluded.A numerical method was developed and accomplished on the commercial software Fluent to investigate the combustion process of ADN-based liquid propellant in the thruster of the attitude control engine.The operating parameters of the thruster in steady operations and pulse operations were calculated and compared with the hot fire test.Then based on their comparisons,the physical and chemical processes of the ADN-based liquid propellant in the thruster were discussed and analyzed.